Protease activities have been implicated in many pathological processes of disease conditions, especially in viral infections. Protease regulators, especially protease inhibitors, are strongly desired for their potential therapeutic applications. For example, because HCV NS3 protease cleaves the non-structural HCV proteins which are necessary for HCV replication, the NS3 protease can be a target for the development of therapeutic agents against the HCV virus. Several methods are available in the field for screening protease inhibitors. However, there is a continuing need in the art to develop more effective methods and reagents for protease regulator screening.